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@@ -66,34 +66,53 @@ gblender_set_gamma_table( double gamma_value, |
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{
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const int gmax = (256 << GBLENDER_GAMMA_SHIFT) - 1;
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double p;
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+ int ii;
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+
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if ( gamma_value <= 0 ) /* special case for sRGB */
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{
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- int ii;
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+ double d;
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+ int linear = 0;
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+
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/* voltage to linear; power function using finite differences */
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- for ( p = gmax, ii = 255; ii > (int)(255.*0.039285714); ii-- )
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+ for ( p = gmax, ii = 255; ii >= 0; ii--, p -= d )
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{
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gamma_ramp[ii] = (unsigned short)( p + 0.5 );
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- p -= 2.4 * p / ( ii + 255. * 0.055 );
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+
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+ if ( linear )
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+ continue;
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+
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+ d = 2.4 * p / ( ii + 255. * 0.055 ); /* derivative */
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+
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+ if ( ii == 10 ) /* same as d < p / ii */
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+ {
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+ d = p / ii;
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+ linear = 1;
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+ }
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}
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- for ( ; ii >= 0; ii-- )
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- gamma_ramp[ii] = (unsigned short)( gmax*ii/(255.*12.92321) + 0.5 );
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+ linear = 0;
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/* linear to voltage; power function using finite differences */
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- for ( p = 255., ii = gmax; ii > (int)(gmax*0.0030399346); ii-- )
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+ for ( p = 255., ii = gmax; ii >= 0; ii--, p -= d )
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{
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gamma_ramp_inv[ii] = (unsigned char)( p + 0.5 );
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- p -= ( p + 255. * 0.055 ) / ( 2.4 * ii );
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+
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+ if ( linear )
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+ continue;
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+
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+ d = ( p + 255. * 0.055 ) / ( 2.4 * ii ); /* derivative */
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+
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+ if ( p < 10.02 ) /* same as d > p / ii */
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+ {
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+ d = p / ii;
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+ linear = 1;
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+ }
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}
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- for ( ; ii >= 0; ii-- )
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- gamma_ramp_inv[ii] = (unsigned char)( 255.*12.92321*ii/gmax + 0.5 );
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}
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else
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{
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- int ii;
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-
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/* voltage to linear; power function using finite differences */
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for ( p = gmax, ii = 255; ii > 0; ii-- )
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{
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